Elevated secretion of myeloperoxidase by neutrophils from asthmatic patients: The effect of immunotherapy

Background: There is increasing evidence of neutrophil participation in ast hma and the allergic process. After activation, neutrophils release myelope roxidase (MPO) together with other granule enzymes, Objectives: In this study we attempted to evaluate the release of MPO in vi tro by neutrophils from asthmatic patients and the relationship between neu trophil degranulation and lung function, measured as FEV1, of the patients. We also investigated the possible role of immunotherapy in the release of MPO by neutrophils, Methods: Neutrophils were stimulated with formyl-methionyl-leucyl-phenylala nine for 45 minutes at 37 degreesC. MPO released from neutrophils was assay ed by using an MPO enzyme immunoassay, Results: Neutrophils released statistically significantly higher MPO levels in the asthmatic patients not receiving immunotherapy than in the healthy group. A significant inverse correlation was observed in the asthmatic grou p not receiving immunotherapy between MPO secretion and lung function, meas ured as FEV1, of the patients. Neutrophils of the asthmatic group receiving immunotherapy released significantly less MPO than did those of the asthma tic group not receiving immunotherapy, with MPO levels equal to those from nonallergic subjects. Conclusions: We conclude that neutrophils obtained from allergic asthmatic patients have an increased propensity to release MPO. The experiments descr ibed here provide evidence that there is a significant inverse relationship between levels of MPO released by neutrophils From allergic patients and l ung function, as assessed by FEV1. Our study suggests that immunotherapy ac tively modifies the release of MPO in vitro by neutrophils from allergic as thmatic patients.